The present invention relates to a golf club head, and more particularly relates to improvements in aerodynamic characteristics of a golf club head.
It is generally known that air current generated around the club head when the golf club is swung has a great influence on the head speed and stability of the swing line.
Conventional golf club heads generally have a hosel of a circular transverse cross-sectional profile. As a result, air current generated near the center of a club head when the head is swung becomes faster than that near the hosel, in particular when the head speed is in a range from 30 to 60 m/sec, and this difference in air current speed generates a sort of bias which urges the head main body to move towards the toe. This bias tends to disturb the stability of the swing line. Further, the circular cross-sectional profile of the conventional hosel forces air current near the hosel to shift from parallel flow to turbulent flow and such current transition induces increased pneumatic resistance, thereby greatly lowering the head speed when the club is swung.
Not only the transverse cross-sectional profile of the hosel but also the entire configuration of the head main body, affects stability of the swing line. In the configuration of a conventional golf club head, the borders between the shooting face, crown face and sole face are demarcated by edge lines having acute angles. The presence of such sharp edge lines greatly disturbs the pneumatic current near the borders when the club is swung and, as a consequence, increases the pneumatic resistance, thereby lowering the head speed. In addition, the loft of the shooting face produces negative buoyancy which is smaller in magnitude than positive buoyancy produced by the crown face and the sole face. Positive buoyancy resulting from this difference greatly disturbs the stability of the swing line.
In an attempt to prevent such current transition, Japanese Patent Publication Sho. 53-31417 proposes to form an elongated groove called a trip step in the upper edge of the shooting face of a golf club head, and Japanese Patent Opening Sho. 62-176469 proposes to form many fine grooves in the crown and sole faces of a golf club head. In practice, however, these prior proposals do not provide a sufficient solution to the problem of aerodynamic characteristics inherent to the conventional golf club head.